Brain Teasers
Perfect Eggs
For his breakfast, Mr Stone likes an egg that has been boiled for exactly 9 minutes. He has two egg timers (those with sand in them), one that runs for 4 minutes and one that runs for 7 minutes. How can he use these timers to boil his egg?
Answer
Start both egg timers. When the 4 minute timer runs out, turn it over. When the 7 minute timer runs out turn it over. When the 4 minute timer runs out again the 7 minute timer has been running for 1 minute. Turn it over once again. When it stops the egg is done.Hide Answer Show Answer
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Comments
really clever! Of course, there are other ways, but yours was the easiest!
this may be easier... Let about half the sand run out of the 4. Then lay it on it's side, so that both piles in each end are the same height. Then put in the egg, run the 7, and THEN run the 4.
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Very clever
Very clever
I got to turn them both over at the same time (without starting the egg). Then turn over the 4 min. as soon as it finishes. When the 7 min. runs out, put the egg in (the 4 has 1 min left). Turn over the 4 when it ends. When 4 ends again, turn it over. When it ends again, the egg is done!
Thought it was a trick question - you can't use timers to boil an egg
Guess I shoulda checked the category
Guess I shoulda checked the category
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